1. Field of the Invention
The present invention relates to methods for correcting an interaxis angle. More particularly, the present invention relates to an improved error measurement method and correction calculation method for eliminating position measurement errors caused by interaxis angle errors in an apparatus having a plurality of axes.
2. Prior Art
In the conventional art, form measuring instrument are used to carry out contour measurement. In order to improve the contour measurement accuracy, it is important to reduce errors. There are many origins of errors, but in multiaxis form measuring instrument, it is particularly important to reduce the errors between individual axial movements.
Thus, in conventional form measuring instrument, the errors between individual axial movements are normally reduced by improving the manufacturing accuracy.
However, in the field of contour measurement, there are demands for measurement apparatus with higher accuracy because of improvements being made in the accuracy of workpieces. In practice, for example, the mechanical manufacturing accuracy of Y-axis tables for measurement apparatuss is limited to about 20 μm/200 mm (about 0.0057 degrees). Higher perpendicularity is required for high accuracy workpieces such as those with aspherical surfaces.
Therefore, in apparatuss for handling high accuracy workpieces, it is essential to further reduce the errors in individual axial movements; however, because the reduction in errors achievable by improving the mechanical manufacturing accuracy is limited, as described above, it is difficult to reduce the errors any further.
In the conventional art, in order to attempt to reduce the effects of such movement errors, the positioning accuracy of each axis of the apparatus is measured based on a calibration gauge.
One error measurement method in the conventional art is a technique for measuring the scale error, straightness, and perpendicularity of the apparatus, for example, with a calibration gauge using a so-called inversion method (see Japanese Unexamined Patent Application Publication No. 2003-302202).
However, in the conventional art described above, it is necessary to position the calibration gauge in the apparatus and to perform measurement and error calculation for the same position before and after inverting the calibration gauge. Therefore, there is still room for improvement in terms of simplifying the measurement procedure.
Also, in the conventional art described above, although the concept of determining correction values based on the error measurement results and correcting the measured values has been conceived, no concrete correction calculation method has yet been established.
Therefore, in the field of multiaxis apparatus, there is an urgent need to develop a technology that will enable a reduction in position measurement errors caused by interaxis angle errors, with higher accuracy and greater ease.